The field of the invention is treatment and prevention of congestive heart failure.
Congestive heart failure, one of the leading causes of death in industrialized nations, results from an increased workload on the heart and a progressive decrease in its pumping ability. Initially, the increased workload that results from high blood pressure or loss of contractile tissue induces compensatory cardiomyocyte hypertrophy and thickening of the left ventricular wall, thereby enhancing contractility and maintaining cardiac function. However, over time, the left ventricular chamber dilates, systolic pump function deteriorates, cardiomyocytes undergo apoptotic cell death, and myocardial function progressively deteriorates.
Factors that underlie congestive heart failure include high blood pressure, ischemic heart disease, exposure to cardiotoxic compounds such as the anthracycline antibiotics, and genetic defects known to increase the risk of heart failure.
Neuregulins (NRGs) and NRG receptors comprise a growth factor-receptor tyrosine kinase system for cell-cell signalling that is involved in organogenesis in nerve, muscle, epithelia, and other tissues (Lemke, Mol. Cell. Neurosci. 7:247-262, 1996 and Burden et al., Neuron 18:847-855, 1997). The NRG family consists of three genes that encode numerous ligands containing epidermal growth factor (EGF)-like, immunoglobulin (Ig), and other recognizable domains. At least 20 (perhaps 50 or more) secreted and membrane-attached isoforms may function as ligands in this signalling system. The receptors for NRG ligands are all members of the EGF receptor (EGFR) family, and include EGFR (or ErbB1), ErbB2, ErbB3, and ErbB4, also known as HER1 through HER4, respectively, in humans (Meyer et al., Development 124:3575-3586, 1997; Orr-Urtreger et al., Proc. Natl. Acad. Sci. USA 90: 1867-71, 1993; Marchionni et al., Nature 362:312-8, 1993; Chen et al., J. Comp. Neurol. 349:389-400, 1994; Corfas et al., Neuron 14:103-115, 1995; Meyer et al., Proc. Natl. Acad. Sci. USA 91:1064-1068, 1994; and Pinkas-Kramarski et al., Oncogene 15:2803-2815, 1997).
The three NRG genes, Nrg-1, Nrg-2, and Nrg-3, map to distinct chromosomal loci (Pinkas-Kramarski et al., Proc. Natl. Acad. Sci. USA 91:9387-91, 1994; Carraway et al., Nature 387:512-516, 1997; Chang et al., Nature 387:509-511, 1997; and Zhang et al., Proc. Natl. Acad. Sci. USA 94:9562-9567, 1997), and collectively encode a diverse array of NRG proteins. The most thoroughly studied to date are the gene products of Nrg-1, which comprise a group of approximately 15 distinct structurally-related isoforms (Lemke, Mol. Cell. Neurosci. 7:247-262, 1996 and Peles and Yarden, BioEssays 15:815-824, 1993). The first-identified isoforms of NRG-1 included Neu Differentiation Factor (NDF; Peles et al., Cell 69, 205-216, 1992 and Wen et al., Cell 69, 559-572, 1992), Heregulin (HRG; Holmes et al., Science 256:1205-1210, 1992), Acetylcholine Receptor Inducing Activity (ARIA; Falls et al., Cell 72:801-815, 1993), and the glial growth factors GGF1, GGF2, and GGF3 (Marchionni et al. Nature 362:312-8, 1993).
The Nrg-2 gene was identified by homology cloning (Chang et al., Nature 387:509-512, 1997; Carraway et al., Nature 387:512-516, 1997; and Higashiyama et al., J. Biochem. 122:675-680, 1997) and through genomic approaches (Busfield et al., Mol. Cell. Biol. 17:4007-4014, 1997). NRG-2 cDNAs are also known as Neural- and Thymus-Derived Activator of ErbB Kinases (NTAK; Genbank Accession No. AB005060), Divergent of Neuregulin (Don-1), and Cerebellum-Derived Growth Factor (CDGF; PCT application WO 97/09425). Experimental evidence shows that cells expressing ErbB4 or the ErbB2/ErbB4 combination are likely to show a particularly robust response to NRG-2 (Pinkas-Kramarski et al., Mol. Cell. Biol. 18:6090-6101, 1998). The Nrg-3 gene product (Zhang et al., supra) is also known to bind and activate ErbB4 receptors (Hijazi etal., Int. J. Oncol. 13:1061-1067, 1998).
An EGF-like domain is present at the core of all forms of NRGs, and is required for binding and activating ErbB receptors. Deduced amino acid sequences of the EGF-like domains encoded in the three genes are approximately 30-40% identical (pairwise comparisons). Further, there appear to be at least two sub-forms of EGF-like domains in NRG-1 and NRG-2, which may confer different bioactivities and tissue-specific potencies.
Cellular responses to NRGs are mediated through the NRG receptor tyrosine kinases EGFR, ErbB2, ErbB3, and ErbB4 of the epidermal growth factor receptor family. High-affinity binding of all NRGs is mediated principally via either ErbB3 or ErbB4. Binding of NRG ligands leads to dimerization with other ErbB subunits and transactivation by phosphorylation on specific tyrosine residues. In certain experimental settings, nearly all combinations of ErbB receptors appear to be capable of forming dimers in response to the binding of NRG-1 isoforms. However, it appears that ErbB2 is a preferred dimerization partner that may play an important role in stabilizing the ligand-receptor complex. Recent evidence has shown that expression of NRG-1, ErbB2, and ErbB4 is necessary for trabeculation of the ventricular myocardium during mouse development.
In view of the high prevalence of congestive heart failure in the general population, it would be highly beneficial to prevent or minimize progression of this disease by inhibiting loss of cardiac function, and ideally, by improving cardiac function for those who have or are at risk for congestive heart failure.
We have found that neuregulins stimulate compensatory hypertrophic growth and inhibit apoptosis of myocardiocytes subjected to physiological stress. Our observations indicate that neuregulin treatment will be useful for preventing, minimizing, or reversing congestive heart disease resulting from underlying factors such as hypertension, ischemic heart disease, and cardiotoxicity.
The invention provides a method for treating or preventing congestive heart failure in a mammal. The method involves administering a polypeptide that contains an epidermal growth factor-like (EGF-like) domain to the mammal, wherein the EGF-like domain is encoded by a neuregulin gene, and wherein administration of the polypeptide is in an amount effective to treat or prevent heart failure in the mammal.
In various preferred embodiments of the invention, the neuregulin gene may be the NRG-1 gene, the NRG-2 gene, or the NRG-3 gene. Furthermore, the polypeptide may be encoded by any of these three neuregulin genes. Still further, the polypeptide used in the method may be recombinant human GGF2.
In another preferred embodiment of the invention, the mammal is a human.
In other embodiments of the invention, the congestive heart failure may result from hypertension, ischemic heart disease, exposure to a cardiotoxic compound (e.g., cocaine, alcohol, an anti-ErbB2 antibody or anti-HER antibody, such as HERCEPTIN(copyright), or an anthracycline antibiotic, such as doxorubicin or daunomycin), myocarditis, thyroid disease, viral infection, gingivitis, drug abuse; alcohol abuse, periocarditis, atherosclerosis, vascular disease, hypertrophic cardiomyopathy, acute myocardial infarction or previous myocardial infarction, left ventricular systolic dysfunction, coronary bypass surgery, starvation, an eating disorder, or a genetic defect.
In another embodiment of the invention, an anti-ErB2 or anti-HER2 antibody, such as HERCEPTIN(copyright), is administered to the mammal either before, during, or after anthracycline administration.
In other embodiments of the invention, the polypeptide containing an EGF-like domain encoded by a neuregulin gene is administered before, during, or after exposure to a cardiotoxic compound. In yet other embodiments, the polypeptide containing the EGF-like domain is administered during two, or all three, of these periods.
In still other embodiments of the invention, the polypeptide is administered either prior to or after the diagnosis of congestive heart failure in the mammal.
In yet another embodiment of the invention, the polypeptide is administered to a mammal that has undergone compensatory cardiac hypertrophy.
In other preferred embodiments of the invention, administration of the polypeptide maintains left ventricular hypertrophy, prevents progression of myocardial thinning, or inhibits cardiomyocyte apoptosis.
In yet another embodiment of the invention, the polypeptide may be administered by administering an expression vector encoding the polypeptide to the mammal.
By xe2x80x9ccongestive heart failurexe2x80x9d is meant impaired cardiac function that renders the heart unable to maintain the normal blood output at rest or with exercise, or to maintain a normal cardiac output in the setting of normal cardiac filling pressure. A left ventricular ejection fraction of about 40% or less is indicative of congestive heart failure (by way of comparison, an ejection fraction of about 60% percent is normal). Patients in congestive heart failure display well-known clinical symptoms and signs, such as tachypnea, pleural effusions, fatigue at rest or with exercise, contractile dysfunction, and edema. Congestive heart failure is readily diagnosed by well known methods (see, e.g., xe2x80x9cConsensus recommendations for the management of chronic heart failure.xe2x80x9d Am. J. Cardiol., 83(2A):1A-38-A, 1999).
Relative severity and disease progression are assessed using well known methods, such as physical examination, echocardiography, radionuclide imaging, invasive hemodynamic monitoring, magnetic resonance angiography, and exercise treadmill testing coupled with oxygen uptake studies.
By xe2x80x9cischemic heart diseasexe2x80x9d is meant any disorder resulting from an imbalance between the myocardial need for oxygen and the adequacy of the oxygen supply. Most cases of ischemic heart disease result from narrowing of the coronary arteries, as occurs in atherosclerosis or other vascular disorders.
By xe2x80x9cmyocardial infarctionxe2x80x9d is meant a process by which ischemic disease results in a region of the myocardium being replaced by scar tissue.
By xe2x80x9ccardiotoxicxe2x80x9d is meant a compound that decreases heart function by directing or indirectly impairing or killing cardiomyocytes.
By xe2x80x9chypertensionxe2x80x9d is meant blood pressure that is considered by a medical professional (e.g., a physician or a nurse) to be higher than normal and to carry an increased risk for developing congestive heart failure.
By xe2x80x9ctreatingxe2x80x9d is meant that administration of a neuregulin or neuregulin-like polypeptide slows or inhibits the progression of congestive heart failure during the treatment, relative to the disease progression that would occur in the absence of treatment, in a statistically significant manner. Well known indicia such as left ventricular ejection fraction, exercise performance, and other clinical tests as enumerated above, as well as survival rates and hospitalization rates may be used to assess disease progression. Whether or not a treatment slows or inhibits disease progression in a statistically significant manner may be determined by methods that are well known in the art (see, e.g., SOLVD Investigators, N. Engl. J. Med. 327:685-691, 1992 and Cohn et al., N. Engl. J Med. 339:1810-1816, 1998).
By xe2x80x9cpreventingxe2x80x9d is meant minimizing or partially or completely inhibiting the development of congestive heart failure in a mammal at risk for developing congestive heart failure (as defined in xe2x80x9cConsensus recommendations for the management of chronic heart failure.xe2x80x9d Am. J. Cardiol., 83(2A):1A-38-A, 1999). Determination of whether congestive heart failure is minimized or prevented by administration of a neurgulin or neuregulin-like polypeptide is made by known methods, such as those described in SOLVD Investigators, supra, and Cohn et al., supra.
By xe2x80x9cat risk for congestive heart failurexe2x80x9d is meant an individual who smokes, is obese (i.e., 20% or more over their ideal weight), has been or will be exposed to a cardiotoxic compound (such as an anthracycline antibiotic), or has (or had) high blood pressure, ischemic heart disease, a myocardial infarct, a genetic defect known to increase the risk of heart failure, a family history of heart failure, myocardial hypertrophy, hypertrophic cardiomyopathy, left ventricular systolic dysfunction, coronary bypass surgery, vascular disease, atherosclerosis, alcoholism, periocarditis, a viral infection, gingivitis, or an eating disorder (e.g., anorexia nervosa or bulimia), or is an alcoholic or cocaine addict.
By xe2x80x9cdecreasing progression of myocardial thinningxe2x80x9d is meant maintaining hypertrophy of ventricular cardiomyocytes such that the thickness of the ventricular wall is maintained or increased.
By xe2x80x9cinhibits myocardial apoptosisxe2x80x9d is meant that neuregulin treatment inhibits death of cardiomyocytes by at least 10%, more preferably by at least 15%, still more preferably by at least 25%, even more preferably by at least 50%, yet more preferably by at least 75%, and most preferably by at least 90%, compared to untreated cardiomyocytes.
By xe2x80x9cneuregulinxe2x80x9d or xe2x80x9cNRGxe2x80x9d is meant a polypeptide that is encoded by an NRG-1, NRG-2, or NRG-3 gene or nucleic acid (e.g., a cDNA), and binds to and activates ErbB2, ErbB3, or ErbB4 receptors, or combinations thereof.
By xe2x80x9cneuregulin-1,xe2x80x9d xe2x80x9cNRG-1,xe2x80x9d xe2x80x9cheregulin,xe2x80x9d xe2x80x9cGGF2,xe2x80x9d or xe2x80x9cp185erbB2 ligandxe2x80x9d is meant a polypeptide that binds to the ErbB2 receptor and is encoded by the p185erbB2 ligand gene described in U.S. Pat. No. 5,530,109; U.S. Pat. No. 5,716,930; and U.S. Ser. No. 08/461,097.
By xe2x80x9cneuregulin-like polypeptidexe2x80x9d is meant a polypeptide that possesses an EGF-like domain encoded by a neuregulin gene, and binds to and activates ErbB-2, ErbB-3, ErbB-4, or a combination thereof.
By xe2x80x9cepidermal growth factor-like domainxe2x80x9d or xe2x80x9cEGF-like domainxe2x80x9d is meant a polypeptide motif encoded by the NRG-1, NRG-2, or NRG-3 gene that binds to and activates ErbB2, ErbB3, ErbB4, or combinations thereof, and bears a structural similarity to the EGF receptor-binding domain as disclosed in Holmes et al., Science 256:1205-1210, 1992; U.S. Pat. No. 5,530,109; U.S. Pat. No. 5,716,930; U.S. Ser. No. 08/461,097; Hijazi et al., Int. J. Oncol. 13:1061-1067, 1998; Chang et al., Nature 387:509-512, 1997; Carraway et al., Nature 387:512-516, 1997; Higashiyama et al., J Biochem. 122:675-680, 1997; and WO 97/09425).
By xe2x80x9canti-ErbB2 antibodyxe2x80x9d or xe2x80x9canti-HER2 antibodyxe2x80x9d is meant an antibody that specifically binds to the extracellular domain of the ErbB2 (also known as HER2 in humans) receptor and prevents the ErbB2 (HER2)-dependent signal transduction initiated by neuregulin binding.
By xe2x80x9ctransformed cellxe2x80x9d is meant a cell (or a descendent of a cell) into which a DNA molecule encoding a neuregulin or polypeptide having a neuregulin EGF-like domain has been introduced, by means of recombinant DNA techniques or known gene therapy techniques.
By xe2x80x9cpromoterxe2x80x9d is meant a minimal sequence sufficient to direct transcription. Also included in the invention are those promoter elements which are sufficient to render promoter-dependent gene expression controllable for cell type or physiological status (e.g., hypoxic versus normoxic conditions), or inducible by external signals or agents; such elements may be located in the 5xe2x80x2 or 3xe2x80x2 or internal regions of the native gene.
By xe2x80x9coperably linkedxe2x80x9d is meant that a nucleic acid encoding a polypeptide (e.g., a cDNA) and one or more regulatory sequences are connected in such a way as to permit gene expression when the appropriate molecules (e.g., transcriptional activator proteins) are bound to the regulatory sequences.
By xe2x80x9cexpression vectorxe2x80x9d is meant a genetically engineered plasmid or virus, derived from, for example, a bacteriophage, adenovirus, retrovirus, poxvirus, herpesvirus, or artificial chromosome, that is used to transfer a polypeptide (e.g., a neuregulin) coding sequence, operably linked to a promoter, into a host cell, such that the encoded peptide or polypeptide is expressed within the host cell.